1. Field of the Invention
The invention relates to an electrical igniter cap which includes a housing, a bursting charge, an igniter unit and an electrical firing device.
2. Discussion of the Prior Art
In accordance with an unpublished data specification sheet an electrical igniter cap comprises a housing which, besides the electrical firing device, contains two igniter charges and a bursting or explosion charge. Those igniter charges involve major fluctuations in terms of firing power and performance. Because of an excessively a id pressure rise and an excessively high gas pressure peak, a large number of cartridge case failures occurred. The igniter unit does not have any cover member so that loosening thereof occurred when drop tests were carried out. Drop tests therefore resulted in the igniter cap being fired.
The object of the invention is to propose an electrical igniter cap which reliably ignites propellent charge powder, which affords a uniform output performance and which is safe.
That object is attained by the invention in that between the bursting charge and the igniter unit there is arranged a sieve plate with a foil of plastic material, which foil is rupture-resistant but tears easily.
In accordance with the invention, no faults occur in the igniter cap after an environmental test such as a jolt test and drop tests. No gap or crack formation occurs, which could result in premature firing. The firing output performance is reproducible. The gas pressure curve is in a range which ensures reliable ignition of the bursting charge comprising propellent charge powder.
Essential aspects in this respect are the sieve or screening plate with sufficiently large gas openings and the plastic sheeting which is resistant to rupture but which tears quickly. The plastic sheeting therefore tears in a defined manner in the cross-sections of the gas openings.
In accordance with a specific feature, the sieve plate bears with a predetermined pressing force against the plastic sheeting causes the igniter unit or composition to bear firmly against the electrical firing device. No crack or gap formation can therefore occur in the region of the igniter unit.
In accordance with another feature, the arrangement has sufficiently large hole cross-sections for the gases of the igniter unit.
The firing wire bridge embedded in the igniter unit, as set forth herein, ensures reliable ignition of the igniter unit. It is enclosed except for the pole surface by the igniter unit. That means that the arrangement affords a large igniter surface area.
In accordance with a specific aspect the plastic foil comprises HDPE (high density polyethylene). It can also comprise another suitable plastic material.